Acetyl cellulose and a process of making the same.



the various therefore,

WILLIAM GODSON LINDSAY, OF NEW YORK, N. Y.,

ASSIG-NOR TO THE CELLULOID COMPANY, A CORPORATION OF NEW JERSEY.

ACETYL GELLULOSE AND A PROCESS OF MAKING THE SAME.

1,236,578. No Drawing.

To all whom it may concern.

Be it. known that 1, WILLIAM GoDsoN LINDSAY, a citizen of the United States, residing at New York, in the county of New York and State of New York, have invented certain new and useful Improvements in Acetyl Cellulose and Processes of Making the Same, of which the following is a full, clear, and exact specification.

This invention relates to acetyl cellulose and a process of making the same. It is well known that while acetyl cellulose is a desirable substance for replacing nitrocellulose in many applications, the special difiiculties connected with its manufacture have, large part, prevented its adoption for practical purposes. The acetylation of cellulose is so sensitive to the influence of acetylizing mixtures and physical conditions that up to the present time it has been hard to produce a definite and uniform product.

The principal difficulty has been the production of acetyl cellulose having a conserved strength of fiber and such a definite solubility as would fit it for use with 'certain solvents, or for applicationto particular purposes in the arts.

Previous to my invention the products of processes proposed have been strictly circumscribed because of their defects orpractical limitations. For example, the acteyl cellulose would be in one case limited to the amorphous form and a definite solubility. In another case the form would be similarly limited, but the solubility would have a wider range. In another case the result would be a fibrous acetyl cellulose, but weak and brittle. In still another case there conservation of the fibrous form, but a limited solubility or degree of.

acetylization.

The varying steps of manufacture are, of extraordinary importance, as they so strongly aifect the final character of the acetyl cellulose. The process which I propose produces acetyl cellulose having new characteristics. In practice ll proceed as follows: I Cellulose, preferably a high grade bleached cotton, is given a preliminary treatment with acetic acid of about 75% \to 98% until the cotton is thoroughly impregnated. The mixture of cotton and acetic acid is a then introducedinto the acetylizing mixture consisting of an acetylating agent Specification of Letters Patent.

Patented Aug. ML, 11% a.

Application filed April 8, 1911. I Serial No. 619,685.

' such as acetic anhydrid, a priming or catasuch as sulfuric acid and a dilulyzing agent ent such as benzene the temperature being from 50 to F., and under certain circumstances 80 F. The temperature of the reaction mixture gradually rises and is then usually maintained at from 70 to 80 F. until the reaction is completed. This takes rom 24 to 30 hours, depending upon the rate of acetylization. By this means I obtain fibrous acetyl cellulose, having a wide range of solubility, such solubility being varied according to the minor conditions of operating hereinafter described. 7

To some extent I control the solubility of my product, either by changing the strength the acetic acid used in the preliminary bath, or by varying the amount of acid used in proportion to the fiber. For example, when using about 200 parts of acid to 100 parts of fiber, I employ acetic acid varying from about 75% to 98%. When using an 85% acetic acid as a constant strength I employ, say from about 7 0 to 250 partsto each 100 parts of the fiber. By this means I can produce an acetyl cellulose soluble in a mixture of chloroform and alcohol, but incompletely soluble in chloroform alone; or a variety which is quite viscous in acetone, or one which produces more fluid solutions. Some of my acetyl cellulose is freely soluble in acetylene tetrachlorid, while some requires the addition of alcohol before the acetylene tetrachlorid will make a. complete solution.

I also vary vents by changes in the proportion of sulfuric acid in the acetylizingmixture, and also by means of time of contact and the temperature, as is generally understood.

So far as I can ascertain, the preliminary treatment above described produces no chemical effect upon the fiber, but simply puts it into'a better condition for the subsequent reaction. Tn other words, when the fiber enters the'acetylizing mixture it is still ordinary cellulose.

T have also discovered certain equivalents of the acetic acid for my preliminary treatment. For example, if the water in the acetic acid be replaced by alcohol, either ethyl or methyl, the effect is apparently the same. These substances may, for lack of a better comprehensive name, be termed herein neutral hydroxyl-containing liquid suh- Y use, say,

stances, both the water and the alcohols being alike in having hydroxyl and alike in their efiect in the process herein disclosed. These substances have the composition shown in the general formula H.C,.H ;..OH where n represents anv integer, such as O, 1, 2, 3, etc. Thus, when n is 2, the formula represents ethyl alcohol. When n is O, the

formula represents water. (Or in place of the acetic acid I can use a mixture of benzol and ethyl or methyl alcohol, in which case the benzol will represent the pure acetic acid, and the alcohol will represent the water. Or the acetic acid can be replaced by ethyl acetate of similar strength; or I may a mixture of ethyl acetate and either ethyl or methyl alcohol, in which case ethyl acetate replaces the pure acetic acid and the alcohols act in place of the Water. In fact, in place of this acetic acid I can use any substance whatever so long as such .substance acts in a similar way to protect the cotton fiber from the initial violent attack of the acetylizing mixture. This protection is afforded by what might be called a diluting or shielding of the cotton fiber by means of a liquidthat'is compatible, but

nevertheless does not readily react with;

acetic anyhdrid and sulfuric acid, but tends to regulate or prolong the initial reaction. Water alone would not be such a liquid, because it would increase the violence of the first attack.

In order to still further instruct the operator, I give the following proportions and conditions as a specific example of my improved process. Upon 100 parts by weight of pure cotton rovings is poured 200 parts acetic acid. After the acid has become uniformly spread throughout the mass, the mixture is introduced into a bath consisting of 600 parts of 96% sulfuric acid, and 1400 parts of benzene, at a temperature/of about F. The acetylation is then allowed to proceed at a temperature of about 70 F. for '24 hours, at the'end of which time, if the conditions given be properly observed, a test portion should be soluble in a-mixture of acetylene tetrachlorid and alcohol, dichlor-' hydrin, epichlorhydrin, or nitrobenzol.

The'excess of the reaction mixture is then removed by any suitable. means; for example, by whizzing or by pressing. The acetyl 'cellulo se is then immersed for one hour in a hot solution of calcium nitrate (consisting of about one pound to the gallon), after which it is thoroughly washed, preferably in hot and then in cold water, and then dried.

The object of this treatment with calcium nitrate is to remove any free sulfuric acid adhering to the fiber, and also to neutralize any sulfonic acid ester thatmight accompany the formatlon of the acetyl cellulose.

parts of acetic anhydrid, 25

then subjecting the The acetyl cellulose produced in this particular instance is, in appearance, quite similar to nitrated cotton in which the strength of the fiber has been retained. That is, it is harsh to the touch and practically as strong as the original cotton fiber. It can be dissolved in a mixture of acetylene tetrachlorid and alcohol or in a mixture of chloroform and alcohol to form a'fiowable solution suitable for the manufacture sheets, or, after being rendered plastic by the addition of the solvents mentioned, it can be manipulated so as to produce other forms. The product is partly but not freely soluble in chloroform alone.

The acetyl'cellulose made by the formula just described has an increase from the cellulose to the final product of about In general, the increase of weight bears some relation to variations in solubility, and depends upon the character of the first solution and the conditions of acetylization. In practice the increase obtained by my process has varied from 50% to 80% and even higher.

As to thisinfiuence of the acetylizing mixture and the conditions of acetylization, I might add that increase in weight is produced by prolonged reaction. The temperature will also have its efiect. But in all cases the influence of the acetic acid into which the cotton is first immersed is greater than of thin the effect of the acetylizing mixture, or time and temperature. ators attention especially to the importance of this first step in my process.

The proportion of sulfuric acid in the acetylizing mixture is also of some .impor; tance in controlling the variety of acetyl cellulose produced. While 1 prefefto use cellulose in the form of cotton, it is understood, of course, that I can use other vegetable fibers'suitably prepared.

The acetyl cellulose made by my process I therefore call the operdoes not consist of any one variety or degree of acetylation. It is not, for example, d1-, or trior tetraacetyl cellulose. And this very mixture or combination is of great practical importance, as furnishing products specially suitable for industrial applications.

Having thus described my invention, I declare that what I claim as new and desire to secure by Letters Patent, is:

1, The process of pr ucing acetyl cellulose which consists in treating cellulose with, a preliminary bath, which, without itself altering the cellulose as such, acts to induce acetylization when the'treated cellulose issubjected to an 'acetylizing bath and which is miscible with the acetylizing bath, and same to the action of a non-solvent acetylizing bath.

2. The process for the manufacture of acetyl cellulose which consists in impregnating cellulose with hydrous acetic acid and acetylization when teasers solvent acetylizing mixture, substantially as described.

3. The process of producing acetyl cellulose which consists in treating'cellulose' with a preliminary bath, which, without itself altering the cellulose as such, acts to induce the treated cellulose is subjected to an acetylizing bath and which is miscible with the acetylizing bath, and then subjecting .the same to the action of an acetylizing mixture.

4;. The process of producing a cellulose derivative which consists in impregnating cellulose with hydrous acetic acid and then subjecting the impregnated cellulose to an esterizing bath.

5. The process of producing acetyl cellulose which consists in treating cellulose with a preliminary bath, which, without itself a1: tering the cellulose as such, acts to induce acetylization when the treated cellulose is subjected to an acetylizing bath and which is miscible with the acetylizing bath, and thensubjecting the same to the action of a non-solvent acetylizing bath, at temperatures ranging from to80 F.

he process for the manufacture of acetyl cellulose which consists in treating cellulose with a liquid miscible with the agents of a non-solvent acetylizing bath, and subjecting the same to an acetylizing mixture of acetic anhydrid, sulfuric acid and benzene at temperatures ranging from 50 to 80 F.

7. The process of producing acetyl cellulose which'consists in treating cellulose with a preliminary bath, which, without itself altering the cellulose as such, acts to induce acetylization when the treated cellulose is subjected to an acetylizing bath, subjecting the same to the action of a non-solvent acetyl zing bath, removing the excess of the acetylizing' mixture, immersing the product in a solution of calcium nitrate, and then washing the same in water. 1

8. The process of producing acetyl cellulose which consists in treatin cellulose with j a preliminary bath, wfich, without itself altering the cellulose as such, acts to induce acetylization when the treated cellulose is subjected to an acetylizing bath, subjecting the same to an acetylizing mixture of acetic anhydrid, sulfuric acid and benzene, removing the excess of the acetylizing mixture, and removing any free acids from the acetylated product.

9. The processfor the manufacture 'of acetyl cellulose which consists intreating cellulose with acetic acid of from 7 5 to 98%, subjecting the sameto an acetylizing mixture of acetic anhydrid, sulfuric acid, and

, benzene at a temperature of from 50 to 80 F, allowing the temperature to rise to from maintaining said latter temperature from 24' to'30 hours, removing mersing the product in a solution of calcium nitrate, and then washing the same in water.

10. The process of manufacturing acetyl cellulose which consists in treating cellulose with hydrous acetic acid, subjecting the same to an acetylizing mixture of acetic anhydrid, sulfuric acid and benzene at temperatures ranging from 50 to 80 F., removing the excess of the acetylizing mixture, and removing any free acids.

he process of producing acetyl cel lulose, which consists in treating cellulose with a preliminary bath, which, without itself altering the cellulose as such, acts to induce ac." t nxiiion when the treated cellulose is subjected to an acetylizing bath and then subjecting the same to the action of an acetylizing mixture of acetic anhydrid, sulfuric acid and benzene.

12. The process for the manufacture of acetyl cellulose which consists in treating 100. parts of cellulose with hydrous acetic acid and then subjecting the same to an acetylizing bath composed of approximately 600 parts of acetic anhydrid, 25 parts of sulfuric acid and 1400 parts of benzene.

13. The process of producing acetyl-cellulose Which consists in treating cellulose with acetic acid of from 75% to 98%, subjecting the same to an acetylizing mixture of acetic anhydrid and benzene, removing the excess of acetylizing mixture and washing the resultant acetyl cellulose.

14. The process of producing acetyl-cellulose which consists in treating cellulose withhydrous acetic acid. subjecting the same to an acetylizing mixure -f acetic anhydrid and benzene, removing the excess of the acetylizing mixture and removing any free acids? I 15. The process of producing acetyl cellulose, which consists in treating cellulose with stantially alter the cellulose as such, and then subjecting the same to the action of a non-solvent acetylating bath, said preliminary bath acting to facilitate acetylation in said later bath.

17 The process of producing acetyl cellulose which consists in treating cellulose with a preliminary bath containing a neutral hydroxyl-containing liquid substance and a diluent therefor which does not substantially liquid substance and a diluent therefor which does not sub-- loo alter the cellulose as such, and then subjecting ' which d not substantially alter the cellulose as such and subjecting such cellulose to an acetylating bath, said first mentioned treatment acting to facilitate acetylationin said bath.

19. The product comprising fibrous cellulose acetate having its orlgmal fibrous cellulose structure unaltered, obtained by impregnating cellulose with a neutral hydroxyl-containing liquid substance and a diluent therefor which do not substantially alter the cellulose as such, and then subjecting the same to the action of an acetylating bath.

20. The product c0mprising fibrous ccllu-- lose acetate having its origlnal fibrous cellulose structure unaltered obtained by impreg-' nating cellulose with hydrous acetic acid and subjecting such cellulose toan acetylating bath of acetic anhydrid and a diluent.

21. The product comprisin fibrous cellulose acetate havin its origimfi fibrous cellu-.

lose structure una tered obtained by impreg "acetylating ing to nating cellulose with hydrous acetic acid and subjecting such cellulose to an acet/ylating bath.

22. The product comprising normal fi brous cellulose acetate, unhydrolyzed, and

having its original fibrous cellulose structure unaltered, said product being soluble 1 in a mixture of acetylene tetrachlorid and alcohol.

' in a mixture of acetylene tetrachlorid and \23. The product comprising normal fibrous cellulose acetate, unhydrolyzed, and

having its original fibrous cellulose structurelunaltered, said .product being soluble alcohol and also in a mixture of chloroform and alcohol. i

2a. The product comprising normal fibrous cellulose acetate, unhydrolyzed, and having its originalfibrous cellulose structure unaltered, saidproduct being soluble in a mixture of acetylene tetrachlorid and alcohol, also in a mixture .of and also soluble, but less readily so, in chloroform alone.

25. The product comprising normal fibrous acetyl cellulose, unhydrolyzed, and having 1178 original fibrous structur e unaltered, and

treated cellulose chloroform and alcohol,

being incompletely soluble in chloroform alone, substantially as set forth.

26. The process of producing acetyl cellulose which consists in treating cellulose with a preliminary bath, which, without itself alterin the cellulose as such, acts to induce acetyllzation and to protect the treated cellulose against too rapid acetylation when it is subjected to an acetylizin bath and which is miscible with the acety izing bath, and then subjecting the same to the action of an acetylizing mixture.

27. The process of producing an acetyl cellulose which consists in treating cellulose with a preliminary bath containing a substance of the composition formula H.C, H .OI-I and a diluent therefor which does not substantially alter the cellulose as such, and then subjecting the same to the action of a non-solvent acetylating bath, said preliminary bath acting to facilitate acetylation in said later bath.

.28. The process of producing acetyl cellulose, which consists in treating cellulose with a preliminary bathfcomprising a liquid substance containing a non-iomzable hy-' droxyl and a diluent for such liquid substance, such bath being ineffective to alter the cellulose. as such, and then subjecting the cellulose to the action of a non-solvent facilitate acetylation in said later bath. i

'29. The rocess which consists in treating cellulose wlth a neutral liquid substance conbath, said preliminary bath acttaining a single hydroxyl in each molecule and a diluent for said substance, such treatment leaving the cellulose substantially unaltered as such, cellulose to an acetylating bath, the initial treatment acting to facilitate acetylation in the later bath. I

30. The process of producing acetyl cellulose, which consists in treating cellulose with a preliminary bath, which, without it and then subjecting such self altering the cellulose 'as such, acts to induce acetylization and to protect the against too rapid acetylization when it is subjected to an acetylizing bath, and then subjecting the same to the action of an acetylizing bath. I

In testimony whereof I afiix my signature,- in presence of two wltnesses.

WILLIAM GODSON LINDSAY.

Witnesses: G. V. EDWARDS, 

